Phytoremediation Applications Research Articles

Uptake patterns of critical metals in alpine plant species growing in an unimpaired natural site

The range of metals used for industrial purposes - electrical engineering, solar panels, batteries - has increased substantially over the last twenty years. Some of these emerging metals are the subject of geopolitical conflict and are considered critical as their unique properties make them irreplaceable. Many of these elements are poorly studied and their biogeochemical cycles still raise many questions. Aim of this study is to analyse the soil-to-plant transfer of some of these chemical elements and to shed light on their uptake pathways.For this purpose, the geological site of Jas Roux (France) was chosen as this alpine site is naturally rich in critical and potentially toxic elements such as As, Sb, Ba and Tl, but nevertheless is host to a high diversity of plants. Elemental concentrations were analysed in the topsoil and in 12 selected alpine plant species sampled in situ. Statistical tools were used to detect species dependent characteristics in elemental uptake.Our analyses revealed accumulation of rare earth elements by Saxifraga paniculata, selective oxyanion absorption by Hippocrepis comosa, accumulation of Tl by Biscutella laevigata and Galium corrudifolium and an exclusion strategy in Juniperus communis. These findings advance our understanding of the environmental behaviour of critical metals and metalloids such as V, As, Y, Sb, Ce, Ba and Tl and might bare valuable information for phytoremediation applications.

Reduction of Cu and nitrate leaching risk associated with EDDS-enhanced phytoextraction process by exogenous inoculation of plant growth promoting rhizobacteria

Biodegradable chelant (S,S)–N,N′-ethylenediaminedisuccinic acid (EDDS) has the more advantages of enhanced metal mobility, rapid degradation, environmental friendliness, and ammonium release. However, the risk of metal and/or nitrate residues and leaching within EDDS biodegradation remains as the bottleneck for the widespread application of EDDS-induced phytoremediation. This study aims to explore if the inoculation of plant growth-promoting rhizobacteria (PGPRs) can eliminate the risk associated with the short-term application of EDDS by investigating Cu phytoextraction and soil nitrate content. Results showed that EDDS application significantly increased the copper (Cu) concentration in shoots, soil total Cu, NH4+-N and NO3−-N content, but decreased plant biomass. The inoculation of PGPRs in the soil showed a strong ability to increase plant biomass, Cu phytoextraction and soil NH4+-N content, and decrease soil Cu and NO3−-N content. Moreover, bacterial dominant taxa were found to be the largest contributors to soil NH4+-N and NO3−-N variation, and the abundance of denitrifying bacteria (Bacteroidetes and Stenotrophomonas) decreased in the treatment with PGPRs. The risk of residual Cu and nitrate leaching was reduced by the inoculation of PGPRs without significantly changing the stability of the bacterial community. These new findings indicate that the exogenous application of beneficial rhizobacteria can provide an effective strategy to reduce the risk in metal-contaminated soils of chelant-assisted phytoextraction.

The Road to Practical Application of Cadmium Phytoremediation Using Rice

Cadmium (Cd) is a toxic heavy metal that causes severe health issues in humans. Cd accumulates in the human body when foods produced in Cd-contaminated fields are eaten. Therefore, soil remediation of contaminated fields is necessary to provide safe foods. Rice is one of the primary candidates for phytoremediation. There is a genotypic variation of Cd concentration in the shoots and grains of rice. Using the world rice core collection, ‘Jarjan’, ‘Anjana Dhan’, and ‘Cho-ko-koku’ were observed with a significantly higher level of Cd accumulation in the shoots and grains. Moreover, OsHMA3, a heavy metal transporter, was identified as a responsive gene of quantitative trait locus (QTL) for high Cd concentration in the shoots of these three varieties likewise. However, it is difficult to apply practical phytoremediation to these varieties because of their unfavorable agricultural traits, such as shatter and easily lodged. New rice varieties and lines were bred for Cd phytoremediation using OsHMA3 as a DNA marker selection. All of them accumulated Cd in the shoots equal to or higher than ‘Cho-ko-koku’ with improved cultivation traits. Therefore, they can be used for practical Cd phytoremediation.

Effects of environmental parameters on Lemna minor growth: An integrated experimental and modelling approach

Pollution of surface waters is a worldwide problem for people and wildlife. Remediation and phytoremediation approaches can offer a solution to deal with specific scenarios. Lemna minor, commonly known as duckweed, can absorb and accumulate pollutants in its biomass. To evaluate if L. minor could be applied for phytoremediation purposes, it is necessary to further investigate its remediation capability and to identify which parameters affect the remediation process. Such a model must include both plant growth and pollutant exchange. A remediation model based on a robust experimental study can help to evaluate L. minor as a proper remediation strategy and to predict the outcome of a L. minor based remediation system. To set up this model, this paper focusses on a detailed experimental study and a comprehensive mathematical modelling approach to represent L. minor growth as a function of biomass, temperature, light irradiation and variable nutrient concentrations. The influence of environmental conditions on L. minor growth was studied, by composing 7 days growth curves. Plants were grown under predefined environmental conditions (25°C, 14h photoperiod, 220 μmol m−2 s−1 light intensity and a modified Hoagland solution with 23.94 mg N L−1 and 3.10 mg P L−1 (N:P ratio of 7.73)) as standard for all experiments. The influence of different temperatures (6, 10, 15, 20, 25, 30 and 35°C), light intensities (63, 118, 170, 220 and 262 μmol m−2 s−1), photoperiods (12h and 14h) and N:P ratios (1.18, 3.36, 7.73 and 29.57) were tested in the model. As a result, a growth model was optimised using separate datasets for temperature, light intensity, photoperiod and nutrients and validated by further integrated testing. The growth model is a stable platform for application in phytoremediation of radionuclides in contaminated water, to be extended in future studies with information of pollutant uptake, pollutant-nutrient interactions and transfer to the biomass.

Applications of phytoremediation to treat reclaimed water in urban parks using aquatic macrophytes

Applications of phytoremediation to treat reclaimed water in urban parks using aquatic macrophytes

Sulfur nanoparticles improved plant growth and reduced mercury toxicity via mitigating the oxidative stress in Brassica napus L.

Experiments were conducted to determine the effects of sulfur nanoparticles (SNPs) on alleviating mercury (Hg) toxicity and accumulation in Brassica napus L. in MS medium. The results demonstrated that 10 mg/L Hg severely inhibit brassica seedlings growth, whereas the addition of 300 mg/L SNPs alleviated Hg toxicity, and dry weight were improved by 42.4% (shoot) and 37.8% (root) compared to 10 mg/L Hg treatment alone. SNPs application decreased Hg accumulation in roots and shoots by 6–10 folds. Comparatively, the effect of corresponding bulk sulfur particles (BSPs) and sulfate as ionic compound for counteracting Hg toxicity and accumulation was less pronounced than SNPs treatment. Co-exposure of SNPs along with Hg also alleviated the Hg-induced oxidative stress as the MDA and H2O2 contents, antioxidant enzymes activities (SOD, POD, APX and GST) and glutathione (GSH) content in roots and shoots were decreased relative to Hg treatment alone. The macro (K, Ca, P, Mg) and micronutrients (Zn, Mn, Fe) concentrations in roots and shoots were elevated considerably by SNPs co-exposure compared to plants exposed to Hg only. Further, the expression of selected genes encoding the antioxidant enzymes and nutrient transporters also showed changes similar to the physiological and biochemical parameters. Our results showed that SNPs play a significant role in the decreasing Hg accumulation, counteracting the Hg toxicity, and enhancing plant biomass and nutrients accumulation in B. napus. These findings will be helpful in developing strategies to decrease heavy metals contamination in the food chain as well as for phytoremediation applications.

Rapid conversion of red mud into soil matrix by co-hydrothermal carbonization with biomass wastes

Red mud is the alkaline and high-volume residue produced from alumina extraction from bauxite ores. Its disposal in purpose-built areas occupies a large amount of land and poses serious threats to surrounding environment. This study proposes an innovative strategy for rapid conversion of red mud into soil matrix by co-hydrothermal carbonization (c-HTC) with biomass wastes. Effective neutralization of the alkalinity is obtained by c-HTC process, lowering the pH from 10.0 to approximate 7.0. Experiments of employing wet biomass wastes, reusing water for c-HTC and long-term pH stability verify the feasibility and practicality of c-HTC process. Change of alkaline components in red mud, formation of hydrochar, and creation of aggregates are revealed by multiple characterizations. As to soil properties, the cation exchange capacity, electrical conductivity, organic carbon, and particle size of c-HTC product is remarkably improved. Perennial ryegrass is well grown in the soil matrix. The c-HTC strategy promotes future application of phytoremediation of red mud at full field scale.

Changes in the Structures and Directions of Heavy Metal-Contaminated Soil Remediation Research from 1999 to 2020: A Bibliometric & Scientometric Study.

The pollution of heavy metals in soil is a problem of great concern to international scholars today. This research investigates the current research activities in the field of soil heavy metal pollution remediation and discusses the current areas of research focus and development trends. We conducted a bibliometric analysis of the literature on soil heavy metal pollution remediation from 1999 to 2020. CiteSpace and Vosviewer were used to conduct document co-citation and cluster analyses on the collected data. The research was mainly carried out based on the following factors: chronological distribution, country and institution distribution, source journal analysis, keyword co-occurrence analysis, and reference co-citation analysis. China (2173, 28.64%) and the United States (946, 12.47%) are the top two countries in terms of the number of articles published, and Environmental Science and Pollution Research (384, 5.06%) and Science of the Total Environment (345, 4.55%) published the most articles. The Chinese Academy of Science (485) is the organization that has contributed the most to the total number of publications. Furthermore, based on a keyword co-word analysis with Vosviewer and CitesSpace, it was concluded that the applications of phytoremediation and biochar in the remediation of heavy metals in soil are current research hotspots. Additionally, future research should focus on repair mechanisms, the development of new repair technology and joint repair systems.

Enhanced biomass and cadmium accumulation by three cadmium-tolerant plant species following cold plasma seed treatment

Cold plasma seed treatment can promote plant growth and enhance the resistance of agricultural crops to adverse stress. However, the effects of plasma seed treatment on the growth and phytoextraction response of plants to cadmium (Cd) remain poorly documented. Here, we have investigated the feasibility of using plasma seed treatment to enhance the biomass and Cd accumulation of three Cd-tolerant species, namely Bidens pilosa L, Solanum nigrum L. and Trifolium repens L, under different plasma treatment conditions. Possible enhancement mechanisms are also proposed according to the levels of organic acids in the roots and the Cd fractions in rhizosphere soil following different plasma treatment conditions. The optimum plasma power was 100 W (B. pilosa) or 500 W (S. nigrum and T. repens). The optimum plasma exposure time for all three species was 60 s. Plasma seed treatment under the optimum treatment conditions enhanced plant dry biomass by ~17.3–45.0% and Cd accumulation by 8.8–54.4% across all three species compared to the controls. Furthermore, the phytoremediation efficiencies, bioaccumulation factors and transfer factors of the three species also increased significantly after seed plasma treatment. The promotion of plasma treatment on the biomass and Cd accumulation of three species might be due to increased exudation of organic acids from the roots into the rhizosphere soil, thus increasing the concentrations of acid-soluble Cd to form Cd-organic acid complexes that facilitated the uptake and translocation of Cd by the plants. Results of this study revealed that cold plasma seed treatment is an environmentally friendly, economical and efficient means to develop the application of phytoremediation for Cd-contaminated soils.

Enhanced phytoremediation of TNT and cobalt co-contaminated soil by AfSSB transformed plant

2,4,6-trinitrotoluene (TNT) and cobalt (Co) contaminants have posed a severe environmental problem in many countries. Phytoremediation is an environmentally friendly technology for the remediation of these contaminants. However, the toxicity of TNT and cobalt limit the efficacy of phytoremediation application. The present research showed that expressing the Acidithiobacillus ferrooxidans single-strand DNA-binding protein gene (AfSSB) can improve the tolerance of Arabidopsis and tall fescue to TNT and cobalt. Compared to control plants, the AfSSB transformed Arabidopsis and tall fescue exhibited enhanced phytoremediation of TNT and cobalt separately contaminated soil and co-contaminated soil. The comet analysis revealed that the AfSSB transformed Arabidopsis suffer reduced DNA damage than control plants under TNT or cobalt exposure. In addition, the proteomic analysis revealed that AfSSB improves TNT and cobalt tolerance by strengthening the reactive superoxide (ROS) scavenging system and the detoxification system. Results presented here serve as strong theoretical support for the phytoremediation potential of organic and metal pollutants mediated by single-strand DNA-binding protein genes. SummarizesThis is the first report that AfSSB enhances phytoremediation of 2,4,6-trinitrotoluene and cobalt separately contaminated and co-contaminated soil.

Development of Phytoremediation Technology For Arsenic Removal-A State of Art

Toxic heavy metals and metalloids, like lead, mercury, arsenic, and selenium, are perpetually free into the surroundings atmosphere. There is a vital need to develop low-priced, effective, and supportable technique for removal or detoxification. Plant primarily based approaches, like phytore mediation, are unit comparatively cheap since they are performed in place and are solar-driven. Now this review, Specific advances in plant-based approaches for the remediation of contaminated water and soil. Phytoremediation is an alternate technology to remove of heavy metals in polluted soil. Wild plants were chosen for arsenic removal experiment. Removal of arsenic by conventional method is very costly; this paper focuses the review on method of phyto remediation to remove arsenic from soil. This method is being aesthetically pleasing and is on average tenfold cheaper than other physical, chemical or thermal remediation methods. This paper attempted to provide a brief review on recent progresses in research and practical applications of phytoremediation for soil and water resources.

Phytoremediation of dairy wastewater using Azolla pinnata: Application of image processing technique for leaflet growth simulation

The present study assessed the phytoremediation efficiency of water fern (Azolla pinnata R.Br.) in the treatment of dairy wastewater (DWW). Batch mode experimentation was done using different dilutions (0 to 100%) of DWW transplanted with five healthy leaflets of A. pinnata. Besides this, the A. pinnata growth was captured using camera vision-based image recognition and further modeled using logistic and modified Gompertz models. The findings showed that after 14 days of phytoremediation experiments, the maximum significant (p < 0.05) reduction efficiency of selected pollutant parameters of DWW i.e. pH (9.41%), electrical conductivity (61.42%), total dissolved solids (71.56%), total Kjeldahl's nitrogen (73.25%), and total phosphorus (65.37%) observed using 75% DWW dilution. Moreover, the periodically taken surface images were useful to recognize the position and number of leaflets which further helped to simulate A. pinnata growth patterns. The maximum number of leaflets (n = 20), fresh biomass (16.18 ± 0.42 g), dry biomass (1.47 ± 0.04 g), and chlorophyll content (3.14 ± 0.03 mg/g fwt.) was also observed using 75% DWW treatment, respectively. The logistic model was found more robust as compared to modified Gompertz to predict leaflet production (y) as revealed from model validation results i.e. coefficient of determination (R2 > 0.9533) and minimum difference between experimental and model-predicted results. Thus, the combined application of phytoremediation and image processing techniques can be used to monitor and maximize plant growth performance.

Dispose waste liquor of fresh biomass of a hyperaccumulator Sedum plumbizincicola in phytoextraction process

Sedum plumbizincicola has been widely employed to remove cadmium (Cd) and zinc (Zn) from contaminated soils and harvested biomass is used to recover valuable metals. While chopping and compacting are efficient methods to rapidly reduce the volume and moisture of fresh biomass, the resulting waste liquor containing metals needs treatment. Two types of contaminated soils were cropped with S. plumbizincicola and top-dressed with this liquor to study metals migration in soil profile and their uptake by plants. There were three treatments: planting and adding liquor (PL), planting without liquor (P) and adding liquor without planting (L). The results showed that Cd and Zn from liquor were mainly retained at top soil 0–10 cm under L treatment. Compared with L treatment, soil Cd and Zn under PL treatment decreased significantly in soil profile due to the extraction of S. plumbizincicola. Moreover, the amount of Cd and Zn extracted by plants was greater than that applied in soils. The metal removal rate by S. plumbizincicola in acid clay loam soil was higher than that in neutral sandy soil. To sum up, metal retaining in soil and uptake by S. plumbizincicola can be used to treat waste liquor from its fresh biomass. Novelty Statement Rapid and efficient treatment of harvested fresh biomass is still a challenge although phytoextraction using hyperaccumulator Sedum plumbizincicola has been widely employed. Chopping and compacting fresh biomass are efficient methods for rapid dehydration, however, a large amount of waste liquor that contains of Cd and Zn is produced and needs treatment. In the present study, a simple and low-cost method was tested to dispose the liquor, i. e. irrigating it onto the surface of contaminated soils where grown S. plumbizincicola. It was found that Cd and Zn applied in soils from liquor were mainly retained at top 0–10 cm soil depth where S. plumbizincicola root system was widespread, and the amount of Cd and Zn extracted by plants was greater than that applied in soils. Therefore, it is technically feasible to dispose the waste liquor dewatering from fresh biomass of S. plumbizincicola in its phytoextraction process. This study is helpful for the rapid, efficient and low-cost treatment of harvested fresh biomass in the large-scale application of phytoremediation.

Effects of Soil Properties on Phytoextraction of Cd and the Associated Soil Bacterial Communities across Four Soil Types

ABSTRACT Soils are one of the repositories for heavy metal. Phytoextraction with hyperaccumulator Tagetes patula (T.patula) has great promise for the cadmium (Cd) removal from contaminated soils. However, there is lack of information about the effects of soil types with different properties on the phytoextraction efficiency and the associated bacterial communities. A pot experiment was performed for 90 d, with four types of soil (black soil, paddy soil, oasis soil, and fluvo-aquic soil) artificially contaminated with Cd at 10 mg kg−1 soil. T.patula showed the greatest Cd uptake efficiency in black soil, followed by paddy soil, oasis soil and fluvo-aquic soil, respectively. Across the four soils, soil pH had the strongest impact on Cd bioaccumulation in T.patula. The Cd uptake amount in T.patula shoot positively correlated with soil CEC, organic matter, total N, total P and total K, and negatively correlated with soil pH and soil particle size. Black soil showed the highest diversity of bacterial community, followed by the paddy, oasis, and fluvo-aquic soils. The structure of communities was altered after phytoremediation albeit to a small degree. Proteobacteria, Acidobacteria, Chloroflexi, Firmicutes, Actinobacteria, Planctomycetes, Gemmatimonadetes, and Bacteroidetes dominated the four soils with different abundances. Soil particle size and CEC had significant negative and positive effects on the richness of the bacterial communities, respectively. These results are important to develop the application of phytoremediation by T. patula in a wide range of Cd-contaminated soils.

Significance of vacuolar proton pumps and metal/H+ antiporters in plant heavy metal tolerance.

Soil and water are among the most valuable resources on earth. Unfortunately, their contamination with heavy metals has become a global problem. Heavy metals are not biodegradable and cannot be chemically degraded; therefore, they tend to accumulate in soils or to be transported by streaming water and contaminate both surface and groundwater. Cadmium (Cd) has no known biological function but is one of the most toxic metals. It represents a serious environmental concern since its accumulation in soils is associated with health risks to plants, animals and humans. On the other hand, copper (Cu) and zinc (Zn) are heavy metals that are indispensable to plants but become toxic when their concentration in soils exceeds a certain optimal level. Plants have evolved many mechanisms to cope with heavy metal toxicity; vacuolar sequestration is one of them. Vacuolar sequestration can be achieved through either phytochelatin-dependent or phytochelatin-independent pathways. Most of the transgenic plants meant for phytoremediation described in the literature result from the manipulation of genes involved in the phytochelatin-dependent pathway. However, recent evidence has emerged to support the importance of the phytochelatin-independent pathway in heavy metal sequestration into the vacuole, with metal/H+ antiporters and proton pumps playing an important role. In this review, the importance of vacuolar proton pumps and metal/H+ antiporters transporting Cd, Cu, and Zn is discussed. In addition, the recent advances in the production of transgenic plants with potential application in phytoremediation and food safety through the manipulation of genes encoding V-PPase proton pumps is described.

Heavy metals accumulation in Nerium oleander leaves across urban areas in Setif region, Algeria

Abstract. Koucim MA, Belguidoum A, Lograda T, Ramdani M. 2021. Heavy metals accumulation in Nerium oleander leaves across urban areas in Setif region, Algeria. Biodiversitas 22: 3083-3091. Pollution by Metallic trace elements (MTE) has become one of the most serious environmental problems resulting from human activity. Plants, which are the base of the food chain, can take up MTE from the soil solution; hyper-accumulators can store high levels of heavy metals in their aerial parts at high concentrations. These plants can be used in phytoremediation. This study aimed to investigate the accumulation of MTE in the leaves of Nerium oleander to monitor environmental pollution of several areas in the province of Setif, Algeria. The samples of N. oleander leaves were collected from 20 urban areas in Setif Province. The concentrations of seven metallic trace elements (Cd, Mn, Pb, Sb, Cu, Bi and Fe) were determined using Flame Atomic Absorption Spectrophotometry (AASF). The results show that the concentrations of heavy metals in the leaves of N. oleander, in general, were very high, far exceeding the certified standard ranges. The order of MTE in the leaves was found as follows: Mn&gt; Sb&gt; Bi&gt; Pb&gt; Fe&gt; Cu&gt; Cd. Our findings indicate that although N. oleander showed a significant capacity to accumulate MTE, the urban areas of Setif province were highly polluted by heavy metals. The presence of metal ions in the aerial parts of the plant indicates that N. oleander is a hyper-accumulator of metals with tolerance to Mn, Sb, and Pb, and can be used as a bio-monitor. This opens up prospects for its application for soil phytoremediation.

STUDI KELAYAKAN TEKNIK DAN BIAYA TERHADAP ALTERNATIF FITOREMIDIASI PADA AIR LIMBAH PENGOLAHAN KOPI

Sidomulyo Village is one of the coffee-producing location s in Silo District, Jember Regency. The coffee processing waste is no handling. Th e co ff ee p ro ce ss in g wa st ew at er could potentially lead to a decrease in environmental quality. Phytoremediation is an alternative technology that can be applied because of the availability of a waste storage pond in Sidomulyo , which ca n to become a pool for phytoremediation. Be si de s, phytoremediation is a simple technology that can reduce the concentration in coffee processing liquid waste. The purpose of this study was to compare phytoremediation alternatives using the aeration, circulation, and constructed wetland (CW) system , which is the most feasible to be applied to coffee processing wastewater treatment in Sidomulyo Village based on tech no lo gy and cost aspects. The stages of this research we re direct surveys of respondents, comparing the efficiency of phytoremediation performance with aeration, circulation and constructed wetland (CW) systems, analysis of techn ic al feasibility, and costs. The research results show that phytoremediation with the CW system is more t ha n feasible than aeration and circulation systems based on technological and cost aspects. Phytoremediation application using the CW system based on the tech no lo gy or technical aspects is more th an feasible because it easy application and has a shorter residence time (continuity). The value of the reduction efficiency of TSS, BOD, and COD parameters in coffee wastewater treatment using phytoremediation with the CW system is sequentially 29.80; 63.75; and 63.70%. Inventory cost of con structing CW for processing coffee wastewater of Rp. 64,050,000 with a storage capacity of 82.5 m 3 .

Comparative transcriptomic analysis reveals the coordinated mechanisms of Populus × canadensis ‘Neva’ leaves in response to cadmium stress

Cadmium (Cd), a heavy metal element has strong toxicity to living organisms. Excessive Cd accumulation directly affects the absorption of mineral elements, inhibits plant tissue development, and even induces mortality. Populus × canadensis ‘Neva’, the main afforestation variety planted widely in northern China, was a candidate variety for phytoremediation. However, the genes relieving Cd toxicity and increasing Cd tolerance of this species were still unclear. In this study, we employed transcriptome sequencing on two Cd–treated cuttings to identify the key genes involved in Cd stress responses of P. × canadensis ‘Neva’ induced by 0 (CK), 10 (C10), and 20 (C20) mg/L Cd(NO3)2 4H2O. We discovered a total of 2,656 (1,488 up-regulated and 1,168 down-regulated) and 2,816 DEGs (1,470 up-regulated and 1,346 down-regulated) differentially expressed genes (DEGs) between the CK vs C10 and CK vs C20, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses in response to the Cd stress indicated that many DEGs identified were involved in the catalytic activity, the oxidoreductase activity, the transferase activity, and the biosynthesis of secondary metabolites. Based on the enrichment results, potential candidate genes were identified related to the calcium ion signal transduction, transcription factors, the antioxidant defense system, and transporters and showed divergent expression patterns under the Cd stress. We also validated the reliability of transcriptome data with the real-time PCR. Our findings deeper the understanding of the molecular responsive mechanisms of P. × canadensis ‘Neva’ on Cd tolerance and further provide critical resources for phytoremediation applications.

Effect of phytoremediation on the shear strength characteristics of silty clayey sand

Pollution of the environment by crude oil is a global problem that changes the geotechnical properties of soil, including its shear strength. In this study, the effects of phytoremediation of soil contaminated with crude oil have been investigated using Ophiopogon japonicus and Platycladus orientalis. The results of phytoremediation were tested at 30 and 60 days of treatment. The results were compared with samples that had not undergone phytoremediation. The soil shear strength parameters were determined using unconsolidated undrained triaxial compression tests at confining pressures of 50, 100, and 150 kPa. The results showed that an increase in the crude oil content led to a decrease in deviatoric stress at failure associated to an axial strain level of 20%. The deviatoric stress in the treated samples was about 15% higher than the samples without phytoremediation. The internal friction angle and cohesion decreased as the crude oil content increased. This decrease was less in the remediated samples, especially those exposed to P. orientalis. The results of the triaxial compression tests revealed the positive effect of phytoremediation in reducing the negative effects of crude oil on the soil shear strength characteristics. SEM images of the contaminated soil samples showed that soil flocculation initially increased with an increase in the crude oil content and time and then decreased subsequent to the application of phytoremediation.

Overexpression of SmZIP plays important roles in Cd accumulation and translocation, subcellular distribution, and chemical forms in transgenic tobacco under Cd stress

Plant ZIP genes represent an important transporter family and may be involved in cadmium (Cd) accumulation and Cd resistance. In order to explore the function of SmZIP isolated from Salix matsudana, the roles of SmZIP in Cd tolerance, uptake, translocation, and distribution were determined in the present investigation. The transgenic SmZIP tobacco was found to respond to external Cd stress differently from WT tobacco by exhibiting a higher growth rate and more vigorous phenotype. The overexpression of SmZIP in tobacco resulted in the reduction of Cd stress-induced phytotoxic effects. Compared to WT tobacco, the Cd content of the root, stem, and leaf in the transgenic tobacco increased, and the zinc, iron, copper, and manganese contents also increased. The assimilation factor, translocation factor and bioconcentration factor of Cd were improved. The scanning electron microscopy and energy dispersive X-ray analysis results of the root maturation zone exposed to Cd for 24 h showed that Cd was transferred through the root epidermis, cortex, and vascular cylinder and migrated to the aboveground parts via the vascular cylinder, resulting in the transgenic tobacco accumulating more Cd than the WT plants. Based on the transverse section of the leaf main vein and leaf blade, Cd was transported through the vascular tissues to the leaves and accumulated more greatly in the leaf epidermis, but less in the leaf mesophyll cells, following the overexpression of SmZIP to reduce the photosynthetic toxicity. The overexpression of SmZIP resulted in the redistribution of Cd at the subcellular level, a decrease in the percentage of Cd in the cell wall, and an increase of the Cd in the soluble fraction in both the roots and leaves. It also changed the percentage composition of different Cd chemical forms by elevating the proportion of Cd extracted using 2% HAc and 0.6 mol/L HCl, but lowering that of the Cd extracted using 1 mol/L NaCl in both the leaves and roots under 10 and 100 μmol/L Cd stress for 28 d. The results implied that SmZIP played important roles in advancing Cd uptake, accumulation, and translocation, as well as in enhancing Cd resistance by altering the Cd subcellular distribution and chemical forms in the transgenic tobacco. The study will be useful for future phytoremediation applications to clean up Cd-contaminated soil.